/dev/sda5 is mounted at '/'. Since that's not set to grow, but instead your actual data storage is mounted at /home and /home2, I would not worry. But, check your '/' area for any files that might be using up that space and delete the unnecessary ones.
Sorry for the inconvenience!
The filesystem mounted at / on this server is running out of disk space. cPanel operations have been temporarily suspended to prevent something bad from happening. Please ask your system admin to remove any files not in use on that partition.